ALD is a deposition method wherein very thin (i.e. atomic) layers of material can be deposited on a surface. ALD tends to be non-selective, i.e., films are deposited conformally on all exposed surfaces.
ALD can be employed at the packing level in the manufacturing of electronic devices to form a coating on the electronic device, wherein the coating serves as a gas, humidity or water-proof barrier layer. Such coatings can be used, for example, in organic light-emitting devices (OLEDs), digital mirror devices (DMDs), micro-electrical-mechanical (MEMS) devices, solar cells, sensors, capacitors and integrated circuit (IC) devices whose operation benefits from being hermetically sealed from the environment. Typical coatings deposited via ALD as a barrier layer include dielectric films such as Al2O3 and TiO2, metallic conductive films like TiN, Pt, Ru, and transparent conductors like indium tin oxide and aluminum doped zinc oxide
Many electronic devices include at least one area that needs to remain uncoated so that it can be accessed. An example of such an area includes contacts pads or contact pins that are used to establish electrical communication between the electronic device and an outside electrical source such as a power source. The contact pads or contact pins need to be exposed so that the electrical contact can be established. This means that the barrier layer or other such layer or layers (e.g., metal and dielectric layers of a capacitor) cannot cover the contact pads or contact pins. This requires either selective removal of the portions of the barrier layer or other such layer that covers the contact pads or contact pins.
The selective removal of a barrier layer has typically been accomplished mechanically or by masking the contact pads or contact pins using masking or dicing tape. These approaches have distinct disadvantages, including damaging the contact pads or contact pins, compromising the quality of the contact, and limiting the temperature of deposition of ALD films.